1. Field of the Invention
This invention relates generally to devices for grading live crawfish according to their size.
2. Prior Art
As with the marketing of any commodity, farmers, producers and distributors are required to comply with certain industry standards relating to quality regarding size, shape, weight, freshness or other such characteristics of the goods. Adherence to these standards is necessary in order to accurately determine the price as well as other conditions of marketing. In the case of produce, various devices have been employed to grade fruits and vegetables, and most have met with great acceptance in that industry. In the marketing of crayfish, however, little has been done to provide an effective grading method, perhaps due to the difficulty in handling these live creatures. Attempts at grading crustaceans have ranged from manual inspection by unskilled laborers to modification of existing produce graders.
One of the methods currently in use involves vibrating a table having spaced-apart horizontal bars wherein the distance between adjacent prongs becomes continuously greater as the crayfish travel horizontally away from the loading area. Another method uses a pair of rotating cylinders spaced apart wherein the distance between the cylinders becomes continuously greater as the crayfish travel away from the loading area. Still another technique for grading crayfish utilizes a single tier of horizontally spaced bars which can be shaken to facilitate the crayfish passing between adjacent bars. The problem with these techniques, however, is that each one fails to yield the consistency and ease of use that are the goals of an effective grading system.
At the present time in Louisiana, there are at least four grades of crayfish based on weight. The first grade (so-called "export" size) are the largest and typically range from 7-14 crayfish per pound. The second grade (so-called "live" size), being slightly smaller, ranges from 15-22 crayfish per pound. The third grade (so-called "processing" size) ranges from 23-30 crayfish per pound, and the fourth grade (so-called "culls") is anything over 30 crayfish per pound. Based on statistical data available to the inventor regarding the growth of crayfish, these grades based on weight are accurately translatable into grades based on size, i.e. physical dimensions, by measurement of the thoracic cavity of the crayfish.
The present invention, therefore, accomplishes a dependable method of grading crayfish using a multiple-tiered grate assembly whose bar spacing is a function of the size of the crayfish thoracic cavity. This invention also helps to alleviate problems seen in the related art by using this grate assembly within a water environment. By simulating their habitat, this novel technique allows the crayfish to seek the lowest possible level on their own within the confines of a static structure, thus resulting in "self-grading" without the need for vibrating trays or rotating parts. Such a design not only speeds up the grading process, but minimizes damage to the crayfish.